Pressure release devices



Sept. 18, 1962 H. c. FOSTER PRESSURE RELEASE DEVICES 3 Sheets-Sheet 1 Filed Aug. 21. 1959 FIG.

INVENTOR.

Sept. 18, 1962 H. c. FOSTER 3,054,350

PRESSURE RELEASE DEVICES Filed Aug. 21, 1959 3 Sheets-Sheet 2 FIG. 3

27 25 f f q 24 2 27 29% E E 31 A 5 I? INVENTOR.

HARRY CLARK FOSTER p 1962 H. c. FOSTER 3,054,350

PRESSURE RELEASE DEVICES Filed Aug. 21, 1959 5 Sheets-Sheet 3 INVENTOR.

HARRY CLARK FOSTER BY 2 1% M ATTORNEYS s tats I the 3,054,350 Patented Sept. 18, 1962 3,054,350 PRESSURE RELEASE DEVICES Harry Clark Foster, East Alton, Ill., assignor to Olin Mathieson Chemical Company, East Alton, 11]., a corporation of Virginia Filed Aug. 21, 1959, Ser. No. 835,230 4 Claims. (Cl. 102-45) This invention relates to pressure release devices and more particularly to such devices adapted to effect the sudden release of a charge of compressed gas to serve as a work performingmedium. While such devices are applicable to many commercial applications, the present invention will be described with particular reference to blasting cartridges utilizing a gas under pressure.

Material breaking cartridges using compressed gas to execute the required work are well known and widely used in the mining industry. Such cartridges or blasting devices are all reliant upon the sudden release of compressed gas to give a quasi explosive effect. The predecessors of this type of blasting cartridges consisted essentially of a cylindrical gas containing cartridge having venting means. The cartridges were charged with gas under considerable pressure, sealed and then conveyed to. the face to be worked. The compressed gas within these cartridges was released by elaborate remote control means. More recently, the practice has been to place an uncharged cartridge in the bore hole and pump gas through a. suitable conduit into the cartridge in situ. conventionally, these cartridges are formed of high strength materials and are. provided vn'th a relatively weak member which shears or ruptures so as to liberate the gas from the cartridge body. Since the amount of pressure that can be built up in the cartridge body is dependent upon the strength of the expendable member, the quantity of energy developed by the liberation of the gas can be controlled within relatively close limits. Such cartridges are generally satisfactory but have one serious inherent drawback. After each shot, the. discharge end of the cartridge must be dismantled to remove the expendable portion which has ruptured or sheared and to replace it with a new one.

This shortcoming has been well recognized and has led to a concerted effort for the development of automatic shells. While many so-called automatic shells have been presented, they have met with only a modicum of success. The previous types of automatic cartridges are operable, but they are very heavy, complex and unreliable. Although the expendable portions of the shell have been eliminated, this elimination has introduced new and more serious problems. Normally, the known automatic shells rely upon a series of two or more control or. pilot valves to initiate the main release valve. Such complexity of design leads to cartridges that are diflicult to control and exceedingly diflicult to discharge at a desired predetermined pressure. In addition, the great number of moving parts in the automatic shells prior. to the advent of the present invention has confronted the industry with a formidable sealing problem. Therefore, it is an object of this invention to provide newand improved automatic or semi-automatic material breaking devices utilizing compressed gas. A further object isto provide a device of this character having novel gas release means. Another object of'this. invention is to provide a simplified automatic or semi-automatic shell overcoming the disadvantages of the prior art.

1The manner in which these and other objects are achieved will be apparent from the following specification together with the drawing in which:

FIGURE 1 is a longitudinal sectional view of a blasting device illustrating an embodiment of the present in-. vention;

FIGURE 2 is a similar view of the device of FIGURE 1' in open position;

FIGURE 3 is a longitudinal sectional view of a blasting device illustrating another embodiment of the present invention;

FIGURE 4 is a similar view of the device of FIGURE 3 in an open position; and

FIGURE 5 is a longitudinal sectional view of still another embodiment of the invention.

The same numbers are used throughout the various figures of the drawing to identify similar components.

Referring to FIGURE 1 which illustrates a preferred embodiment of the invention, an elongated tubular body formed of metal of a strength to contain gas under high pressures, for example 6,000 to 20,000 pounds per square inch, is indicated generally at 1. Suitable means are provided at one end of the cartridge for introducing compressed gas into it. Such means are indicated at 2. The outer diameter of the body is such that it may be set freely within a bore drilled in the face of the material to be mined. The end of the body remote from the gas inlet is closed with an end cap 3 which is screw threadedly attached to the body as shown at 4. The end cap is provided with a plurality of lateral outlet ports 5. These ports are normally closed by valve 6 which is slidable within the cartridge. The interior of the end cap 3 is stepped as shown at 7 and is provided with. a tapered valve seat 8. From the drawing, it will be noted that both ends of valve 6 are exposed to the pressure within the chamber 9 and that the diameter of the valve at end10 remote from the end cap is slightly less than the diameter of that portion of the valve engaged with the beveled valve seat 8. Thus, while the cartridge is being charged with compressed gas, this differential area tends to urge the valve to the left. This tendency is normally overcome by helical spring 11. The tapered forward face 12 of valve 6 cooperates with the stepped portion 7 of the end cap to form an annular obturated chamber 13.

The end cap 3 is provided with a central aperture in which reset button 14 provided with sealing O-ring 15 is positioned. The reset button is provided with an annular flange 16 and terminates in tapered portion 17. The tapered portion of the reset button cooperates with slot 18 in latch bar 19 which is held in place by fixture 20. Compression spring 21 is positioned between the latch bar and fixture as shown. The tension on spring 11 is readily controlled by the screw thread attachment 4 between body 1 and end cap 3. The relative position of these two elements is maintained by lock ring 37.

In operation, compressed air or other suitable gas is introduced into main chamber 9 through gas inlet 2. During charging, both ends of the main valve are subjected to the pressure within the main chamber. Since the end of the valve proximate the end cap '3 has a greater effective area than the remote end '10 of the valve, the pressure in the chamber has atendency to force the valve away from valve seat 8. This tendency is overcome by the helical spring 11 until the pressure in the chamber approaches the predetermined discharge pressure. At this point, the excess in force due to air pressure on the end of the valve near the end cap equals or overcomes the force of the spring 11. The valve is then unse'ated from beveled valve seat 8 and that portion of the valve in the obturated annular chamber .13 is also subjected to the force of the compressed gas in the main chamber. Thus, the effective area of the valve at this end is suddenly and substantially increased. This suddenv increase in the effective area of the valve proximate theports causes the valve to slide very rapidly to the left so as to open ports 5 and permit the charge of compressed gas inchamber 9 to escape very rapidly.

As shown in FIGURE 2, when the valve 6 moves to the left, latch bar 19 is moved by helical spring 21 into the path of the valve. Thus, the latch bar effectively prevents complete reclosing of the valve and eliminates the hazard of premature recharging of the cartridge. When the next charge is to be fired in the cartridge, the latch bar 19 is returned to its original position by pressing or tapping inwardly on reset button 14. The valve is then returned to a closed position by spring 11 and the cartridge is again ready for charging.

In the embodiment shown in FIGURES 3 and 4, the lateral discharge ports 5 have been moved to a more central position and the valve 6 opens by sliding to the right rather than to the left. The valve is provided with an internal annular flange 18 and an external skirt 19 to obstruct entrance of dirt through the ports 5. End cap 3 is provided with reset button 14 which has a central cavity 20. Mounted within the end cap is fixture 21 having a plunger 22 mounted in a central passageway therein. The enlarged terminal portions 23 and 24 of plunger 22 cooperate respectively with helical spring 25 and cammed latches 26. The latches are mounted in fixture 21 by means of pins 27. The external portions of latches 26 are provided with toothed sections 28 which rest against the internal flange 18 of the valve when it is in a closed position. The valve 6 terminates at the left end in a stepped portion 29 which cooperates with ring 30 to form an obturated annular chamber 31 between the valve and the ring.

In the operation of the embodiment of FIGURES 3 and 4, the valve 6 is again urged away from the ports 5 as the gas pressure builds up Within chamber 9' because the valve has a greater efiective area on the left hand .end than on the right hand end. This tendency is overcome by helical spring '11 until a predetermined discharge pressure is built up. At this point, when the force of spring 11 is at least equalized, valve 6 is unseated from ring 30 and the obturated annular space 31 is then subjected to the pressure within the main chamber. Thus, the effective area of the left hand end of the valve is abruptly increased to a value much greater than the effective area on the right hand side of the valve. This sudden increase in the effective cross-sectional area of the left hand side of the valve causes it to open very rapidly and the compressed gas within chamber 9 is suddenly and efiectively discharged through ports 5.

When valve 6 is in a closed position, the enlarged terminal portion 24 of shaft 22 has a cam action on latches 26 due to spring 25. However, this tendency of the latches to extend outwardly is overcome by their contact with valve 6. It will be noted that the pressure on either end of shaft 22 is equalized by means of one or more passageways 39 through fixture 21. As shown in FIGURE 4, when the valve opens, the toothed portion 28 of latches 26 extends outwardly beyond flange 18 of the valve and holds it in a partially open position. This insures complete discharge of the gas in the main chamber and also prevents premature recharging. The cartridge is returned to a firing condition by applying pressure to or tapping reset button 14. This forces shaft 22 to the left and permits latches 26 to converge about the shaft and allows the valve 6 to return to a closed position. Reset button 14 also serves as an indicator since it moves to an outward position when gas pressure is built up within the cartridge.

The embodiment shown in FIGURE 5 is somewhat similar to the embodiment of FIGURE 3 but presents the invention in a more simplified form. In this embodiment, valve 6 is urged into a seating position with valve seat 80 by centrally located helical spring on spring mount 32. It will be noted that the spring mount is adjustable by means of adjustment screw 33 passing through end cap 3 and provided with lock nut 34. The adjustment screw 33 is sealed to the end cap by O-ring 37 in internal extension 38 of the end cap. The pressure on either end of the spring is maintained substantially equal by means of passageway 35 through the valve and the valve is sealed to the end cap by O-ring 36. Here again, valve seat 30 and the left hand end of the valve cooperate to form an annular obturated chamber 3 1 which has an outside diameter much greater than the right hand end of the valve. It will also be noted from FIGURE 5 that the internal diameter of the valve seat 30 is also slightly larger than the diameter of the valve at the end remote from the annular ring.

A pressure is built up in chamber 9, valve 6 is urged to the right into an open position because of its diflerential areas. This tendency is overcome by spring 11 until the pressure within chamber 9 approximates the predetermined discharge pressure. At this point, the seating force imparted by the spring is at least equalized by the differential forces on the valve and that portion of the valve in the annular obturated space is then also subjected to the pressure within the main chamber. Thus, here again, the valve is abruptly forced to the right away from the ports so as to provide efiicient discharge of the compressed gas in chamber 9. The cartridge of this embodiment is fully automatic. After the charge of compressed gas is expelled from chamber 9 through ports 5, valve 6 is returned to a closed position and the cartridge is ready to be recharged.

While the invention has been described with particular reference to blasting or coal breaking cartridges, it will be readily appreciated that it is also applicable to any pressure release device in which a charge of compressed gas is suddenly liberated to act as a work performing medium. Such devices include metal working and shaping devices, cutting devices, power cartridges, and the like.

Although the invention has been described in considerable detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that many modifications can be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A blasting device comprising a cartridge having a substantially cylindrical chamber having a substantially cylindrical side wall and adapted to contain a charge of compressed gas, a gas inlet at one end of the chamber, lateral gas outlets intermediate the ends of the chamber and passing through the side wall thereof, an internal annular constriction rigidly mounted within the chamber adjacent the outlets and between the outlet and the inlet, a substantially cylindrical main valve adapted to close said outlets during charging of the chamber, one end of said valve having a first portion with a diameter greater than the internal diameter of the constriction and a second portion adjacent the constriction having a diameter less than the internal diameter of the constriction, the main valve being a pressure responsive differential sleeve valve normally urged to the open position by pressure within the chamber uniformly applied'to both ends of the main valve and adapted during charging to span and close the outlet and to seat against the constriction to form an annular sealed chamber enclosing said first portion of said valve between the valve and the constriction, the cross sectional area of the main valve exposed to the pressure in the cylinder being greater at the end of the valve adjacent the constriction than at the opposite end of the main valve, and resilient means restraining the valve in a closed position against the constriction during charging of the chamber, said second portion of the main valve being the greater area exposed to the pressure in the chamber during charging of the cartridge.

2. A blasting device in accordance with claim 1 in which the diameter of-that portion of the valve adjacent the constriction is at least equal to the diameter of the other end of the valve, and in which the outside diameter of the annular sealed chamber is substantially greater than the diameter of the other end of the valve.

3. A blasting device comprising a cartridge having a substantially cylindrical chamber for containing a charge of compressed gas, a gas inlet at one end of the chamber, lateral gas outlets intermediate the ends of the chamber, an internal annular constriction rigidly mounted within the chamber adjacent the outlets and between the outlet and the inlet, a main valve slidable in the chamber and having a diameter greater than the constriction with the portion of the valve adjacent the constriction having a diameter less than the internal diameter of the constriction, and a portion of the valve remote from the constriction having a diameter less than the constriction, the valve being a pressure responsive differential valve normally urged to the open position by pressure in the chamber uniformly applied to both ends of the main valve and adapted during charging to span and close the outlet and to seat against the constriction to form an annular sealed chamber between the valve and the constriction, and resilient means restraining the valve in a closed position against the constriction during charging of the chamber, the cross sectional area of the main valve exposed to the pressure in the cylinder being greater at the end of the valve adjacent the constriction than at the opposite end of the main valve, the compressed gas in the chamber during charging exerting a greater force on the end of the value adjacent the constriction than on the end remote therefrom and less than the total force exerted on the remote end by the compressed gas and by the resilient means, the force on the reduced portion of the valve adjacent the constriction being at least equal to the entire force exerted on the remote end of the valve by the pressure in the chamber and by the spring at a predetermined discharge pressure.

4. A blasting device comprising a cartridge having a substantially cylindrical chamber therein having a substantially cylindrical side wall and adapted to receive a charge of compressed gas, gas inlet means at one end of the chamber, lateral discharge outlets passing through the side wall of the chamber intermediate its ends, an annular internal constriction rigidly secured within the chamber adjacent the outlets and between the outlets and the other end of the cylinder, a substantially cylindrical pressure responsive main valve having a greater diameter than the internal diameter of the constriction, the front face of said valve being tapered and seated on said constriction so that a narrowed first portion of said front face is exposed to the pressure in the chamber and a second portion of said front face is positioned in a sealed annular chamber formed between the constriction and the valve, the cross-sectional area of said first portion exposed to the pressure in the chamber being greater than the area exposed to said pressure at the opposite end of said valve, said pressure responsive main valve being urged into an open position by the pressure in the chamber being exerted uniformly on both ends of the main valve during charging of the chamber thereby exerting a greater force on the end having a greater cross-sectional area exposed to said pressure, resili ent means opposing said movements toward the open position and restraining the valve in a closed position spanning the outlets, the sum of the areas of said first and second portions of said front face of the valve being much greater than the effective cross-sectional area on the other end of the valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,502,694 Armstrong Apr. 4, 1950 2,504,470 Trautman Apr. 18, 1950 2,720,167 Hesson Oct. 11, 1955 2,771,032 Callahan Nov. 20, 1956 3,016,015 Filstrup Jan. 9, 1962 

